This invention relates to the discovery and asexual propagation of a new variety of grapevine, Vitis vinifera cv. xe2x80x98Sugratwentyxe2x80x99. The new variety was first hybridized by David W. Cain in Wasco, Kern County, Calif., the variety being originated by controlled hybridization. The new variety is characterized by producing red, obovate, extremely crisp, medium sized seedless berries which increase in size in response to exogenously applied gibberellic acid. The new variety produces very large, naturally loose clusters and is extremely productive when spur pruned.
The seed parent is the xe2x80x98Christmas Rosexe2x80x99 (U.S. Plant Pat. No. 5,056) variety. The pollen parent is the xe2x80x98U.S. Department of Agriculture selection B31-164xe2x80x99 variety. The parent varieties were first crossed in May, 1989, with the date of first flowering being May, 1991. The new xe2x80x98Sugratwentyxe2x80x99 variety was first asexually propagated by David W. Cain near Wasco, Kern County, Calif., in December, 1991 by using cuttings.
The new grapevine variety cv. xe2x80x98Sugratwentyxe2x80x99 resembles its seed parent the xe2x80x98Christmas Rosexe2x80x99 in outward appearance. It differs from the xe2x80x98Christmas Rosexe2x80x99 variety by possessing vestigial seed traces rather than fully developed, hard seeds. It also differs from its seed parent the xe2x80x98Christmas Rosexe2x80x99 by having smaller berries which color with more difficulty. The new variety xe2x80x98Sugratwentyxe2x80x99 differs from its pollen parent, the unnamed, nonpatented xe2x80x98B31-164xe2x80x99 by having smaller, less-lignified seed remnants and obovate rather than round berries which ripen later.
xe2x80x98Sugratwentyxe2x80x99 is distinguished from other commonly grown red seedless grapes such as the xe2x80x98Crimsonxe2x80x99 (nonpatented) variety and the xe2x80x98Ruby Seedlessxe2x80x99 (nonpatented) variety. The new variety xe2x80x98Sugratwentyxe2x80x99 most nearly resembles the xe2x80x98Crimsonxe2x80x99 variety, but differs from xe2x80x98Crimsonxe2x80x99 by possessing a more fruitful but less vigorous vine. The berries of xe2x80x98Sugratwentyxe2x80x99 are more broadly obovate than the narrow, elongated, cylindrical berries of xe2x80x98Crimsonxe2x80x99. Additionally, xe2x80x98Sugratwentyxe2x80x99 produces clusters that are larger and looser than in the xe2x80x98Crimsonxe2x80x99 variety.
The new variety xe2x80x98Sugratwentyxe2x80x99 differs from the xe2x80x98Ruby Seedlessxe2x80x99 variety by producing larger, firmer berries. It also is distinguished from the xe2x80x98Ruby Seedlessxe2x80x99 variety in that the berries attain a much brighter, less blackish-red coloration but are more difficult to color than the berries of the xe2x80x98Ruby Seedlessxe2x80x99 variety.
The new xe2x80x98Sugratwentyxe2x80x99 variety has been shown to maintain its distinguishing characteristics through successive propagations by, for example, cuttings.